Flexible display device having a multi-thickness function layer

ABSTRACT

A flexible display device includes a flexible display panel having a bending area to be folded, and including a display substrate, and a thin-film encapsulation layer above the display substrate, a driving portion, and a function layer below the flexible display panel, and including a step portion below which the flexible display panel is electrically connected to the driving portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/271,579, filed Feb. 8, 2019, which is a continuation of U.S. patentapplication Ser. No. 15/456,336, filed Mar. 10, 2017, now U.S. Pat. No.10,236,471, which claims priority to and the benefit of Korean PatentApplication No. 10-2016-0029668, filed Mar. 11, 2016, the entire contentof all of which is incorporated herein by reference.

BACKGROUND 1. Field

One or more embodiments relate to a flexible display device.

2. Description of the Related Art

In general, display devices are used in mobile devices, such assmartphones, laptop computers, digital cameras, camcorders, portableinformation terminals, or tablet personal computers, or are used inelectronic devices, such as desktop computers, televisions, outdooradvertising plates, or display devices for exhibitions.

Recently, slim display devices have been commercially available.

Flexible display devices may be more easily moved, and may be applicableto various devices. A representative example of a flexible displaydevice is an organic light-emitting display technology-based flexibledisplay device.

SUMMARY

Embodiments of the present disclosure provide a flexible display devicecapable of reducing a bezel.

Additional aspects will be set forth in part in the description thatfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

According to one or more embodiments, a flexible display device includesa flexible display panel having a bending area to be folded, andincluding a display substrate, and a thin-film encapsulation layer abovethe display substrate, a driving portion, and a function layer below theflexible display panel, and including a step portion below which theflexible display panel is electrically connected to the driving portion.

The function layer may include a first surface facing the flexibledisplay panel, a second surface opposite to the first surface, and aside surface connecting the first surface and the second surface,wherein a thickness of the step portion is less than a thickness of aremainder of the function layer with respect to a direction from thesecond surface of the function layer to the first surface of thefunction layer.

A pad terminal on the flexible display panel may be connected to adriving terminal on the driving portion below the step portion.

A portion at which the flexible display panel may be connected to thedriving portion might not extend beyond the second surface of thefunction layer.

The driving portion may include a flexible film, and a drivingintegrated circuit (IC) located on the flexible film, wherein thedriving terminal is located at an edge of the flexible film andcorresponds to the pad terminal.

A portion of the flexible display panel may pass by the side surface ofthe function layer.

The function layer may include an extension portion extending from theside surface of the function layer, and contacting an inner surface ofthe flexible display panel at the bending area.

A curvature of an edge of the extension portion may correspond to acurvature of the flexible display panel at the bending area.

A filling material may fill a space between the flexible display panelat the bending area and the side surface of the function layer.

The flexible display device may further include a support layer betweenthe flexible display panel and the function layer.

A Young's modulus of the support layer may be 10 MPa or more, and athickness of the support layer may be about 5 micrometers or less.

The function layer may include a cushion layer between the flexibledisplay panel and the driving portion, and a heat dissipation layer atan outermost surface of the function layer.

The cushion layer may include a polymer as a foam, a gel, or a rubber.

A Young's modulus of the cushion layer may be 10 MPa or less.

The cushion layer may include graphite particles or a black material.

The function layer may include a graphite layer or a black layer on asurface of the cushion layer.

The function layer further may include an embossing layer between theflexible display panel and the cushion layer, and a surface of theembossing layer facing the flexible display panel may define a pluralityof air discharge indentations.

The flexible display panel may include a first surface below thethin-film encapsulation layer, and a second surface facing the functionlayer.

The flexible display panel may be bent away from the thin-filmencapsulation layer at the bending area.

A curvature of the flexible display panel at the bending area maycorrespond to a thickness of the step portion of the function layer.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of the embodiments, taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of a flexible display device according toan embodiment, the flexible display device being unfolded;

FIG. 2 is a perspective view of the flexible display device FIG. 1, theflexible display device being folded;

FIG. 3 is an exploded plan view of a flexible display device accordingto an embodiment;

FIG. 4 is a cross-sectional view of the flexible display device of FIG.3 being assembled;

FIG. 5 is a cross-sectional view of an example of the flexible displaydevice of FIG. 4;

FIG. 6 is a cross-sectional view illustrating a portion of a functionlayer according to an embodiment;

FIG. 7 is a cross-sectional view illustrating a portion of a functionlayer according to an embodiment;

FIG. 8 is a cross-sectional view of an assembled flexible display deviceaccording to an embodiment;

FIG. 9 is a cross-sectional view of an assembled flexible display deviceaccording to an embodiment; and

FIG. 10 is a cross-sectional view of a sub-pixel of an organiclight-emitting display device according to an embodiment.

DETAILED DESCRIPTION

Features of the inventive concept and methods of accomplishing the samemay be understood more readily by reference to the following detaileddescription of embodiments and the accompanying drawings. Hereinafter,example embodiments will be described in more detail with reference tothe accompanying drawings, in which like reference numbers refer to likeelements throughout. The present invention, however, may be embodied invarious different forms, and should not be construed as being limited toonly the illustrated embodiments herein. Rather, these embodiments areprovided as examples so that this disclosure will be thorough andcomplete, and will fully convey the aspects and features of the presentinvention to those skilled in the art. Accordingly, processes, elements,and techniques that are not necessary to those having ordinary skill inthe art for a complete understanding of the aspects and features of thepresent invention may not be described. Unless otherwise noted, likereference numerals denote like elements throughout the attached drawingsand the written description, and thus, descriptions thereof will not berepeated. In the drawings, the relative sizes of elements, layers, andregions may be exaggerated for clarity.

It will be understood that, although the terms “first,” “second,”“third,” etc., may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are used to distinguish one element, component, region,layer or section from another element, component, region, layer orsection. Thus, a first element, component, region, layer or sectiondescribed below could be termed a second element, component, region,layer or section, without departing from the spirit and scope of thepresent invention.

Spatially relative terms, such as “beneath,” “below,” “lower,” “under,”“above,” “upper,” and the like, may be used herein for ease ofexplanation to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. It will beunderstood that the spatially relative terms are intended to encompassdifferent orientations of the device in use or in operation, in additionto the orientation depicted in the figures. For example, if the devicein the figures is turned over, elements described as “below” or“beneath” or “under” other elements or features would then be oriented“above” the other elements or features. Thus, the example terms “below”and “under” can encompass both an orientation of above and below. Thedevice may be otherwise oriented (e.g., rotated 90 degrees or at otherorientations) and the spatially relative descriptors used herein shouldbe interpreted accordingly.

It will be understood that when an element, layer, region, or componentis referred to as being “on,” “connected to,” or “coupled to” anotherelement, layer, region, or component, it can be directly on, connectedto, or coupled to the other element, layer, region, or component, or oneor more intervening elements, layers, regions, or components may bepresent. In addition, it will also be understood that when an element orlayer is referred to as being “between” two elements or layers, it canbe the only element or layer between the two elements or layers, or oneor more intervening elements or layers may also be present.

In the following examples, the x-axis, the y-axis and the z-axis are notlimited to three axes of a rectangular coordinate system, and may beinterpreted in a broader sense. For example, the x-axis, the y-axis, andthe z-axis may be perpendicular to one another, or may representdifferent directions that are not perpendicular to one another.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentinvention. As used herein, the singular forms “a” and “an” are intendedto include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes,” and “including,” when used inthis specification, specify the presence of the stated features,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items. Expressionssuch as “at least one of,” when preceding a list of elements, modify theentire list of elements and do not modify the individual elements of thelist.

As used herein, the term “substantially,” “about,” and similar terms areused as terms of approximation and not as terms of degree, and areintended to account for the inherent deviations in measured orcalculated values that would be recognized by those of ordinary skill inthe art. Further, the use of “may” when describing embodiments of thepresent invention refers to “one or more embodiments of the presentinvention.” As used herein, the terms “use,” “using,” and “used” may beconsidered synonymous with the terms “utilize,” “utilizing,” and“utilized,” respectively. Also, the term “exemplary” is intended torefer to an example or illustration.

When a certain embodiment may be implemented differently, a specificprocess order may be performed differently from the described order. Forexample, two consecutively described processes may be performedsubstantially at the same time or performed in an order opposite to thedescribed order.

The electronic or electric devices and/or any other relevant devices orcomponents according to embodiments of the present invention describedherein may be implemented utilizing any suitable hardware, firmware(e.g. an application-specific integrated circuit), software, or acombination of software, firmware, and hardware. For example, thevarious components of these devices may be formed on one integratedcircuit (IC) chip or on separate IC chips. Further, the variouscomponents of these devices may be implemented on a flexible printedcircuit film, a tape carrier package (TCP), a printed circuit board(PCB), or formed on one substrate. Further, the various components ofthese devices may be a process or thread, running on one or moreprocessors, in one or more computing devices, executing computer programinstructions and interacting with other system components for performingthe various functionalities described herein. The computer programinstructions are stored in a memory which may be implemented in acomputing device using a standard memory device, such as, for example, arandom access memory (RAM). The computer program instructions may alsobe stored in other non-transitory computer readable media such as, forexample, a CD-ROM, flash drive, or the like. Also, a person of skill inthe art should recognize that the functionality of various computingdevices may be combined or integrated into a single computing device, orthe functionality of a particular computing device may be distributedacross one or more other computing devices without departing from thespirit and scope of the exemplary embodiments of the present invention.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which the present invention belongs. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and/orthe present specification, and should not be interpreted in an idealizedor overly formal sense, unless expressly so defined herein.

FIG. 1 is a perspective view of a flexible display device 100 accordingto an embodiment, the flexible display device being unfolded, and FIG. 2is a perspective view of the flexible display device FIG. 1, theflexible display device being folded.

Referring to FIGS. 1 and 2, the flexible display device 100 includes aflexible display panel 110. The flexible display panel 110 includes anactive area (AA) 111 for displaying an image, and an inactive area (IA)112 extending from the AA 111.

The flexible display panel 110 includes a flexible display substrate,and also includes various films, such as a touch screen, a planarizingplate, a cover window, etc.

An image displayed on the flexible display device 100 may be viewedwhile the flexible display device 100 is in various forms, for example,while flexible display device 100 is spread out, curved, or rolled to bein a cylindrical form.

FIG. 3 is an exploded plan view of a flexible display device 300according to an embodiment, and FIG. 4 is a view of the flexible displaydevice 300 of FIG. 3 being assembled.

Referring to FIGS. 3 and 4, the flexible display device 300 includes aflexible display panel 310, a driver (e.g., a driving unit) 350electrically connected to the flexible display panel 310, and a functionlayer 340 located below the flexible display panel 310.

In the present embodiment, an organic light-emitting display device isused as the flexible display device 300. In other embodiments, theflexible display device 300 may be a liquid crystal display (LCD), afield emission display (FED), an electronic paper display (EPD), or thelike.

The flexible display panel 310 includes a display substrate 311including a plurality of devices, and a thin film encapsulation (TFE)layer 312 located on the display substrate 311.

The flexible display panel 310 includes a first surface 310 a, and asecond surface 310 b that is opposite to the first surface 310 a. Thesecond surface 310 b may face the function layer 340. The TFE layer 312may be located on the first surface 310 a of the flexible display panel310.

A planarizing plate 330 may be located above the flexible display panel310. In one or more embodiments, a touch screen or a cover window may befurther located on the flexible display panel 310. An adhesion layer 371may be located between the flexible display panel 310 and theplanarizing plate 330.

The flexible display panel 310 includes an AA 313 for displaying animage, and an IA 314 extending from the AA 313.

The IA 314 surrounds the AA 313. The IA 314 includes a bending area (BA)315 allowing the flexible display panel 310 to be folded. In oneembodiment, the flexible display panel 310 includes a pad area (PA) 316extending from the BA 315.

At least one thin film transistor (TFT) and at least one light-emittingdevice connected thereto may be located on the display substrate 311.The display substrate 311 may include a polymer, such as polyimide (PI).

The TFE layer 312 may be located above the display substrate 311. The AA313 may be covered by the TFE layer 312.

The BA 315 may be folded away from, or in a direction opposite to, thefirst surface 310 a of the flexible display panel 310 with the TFE layer312 thereabove.

The PA 316 may be located at an edge of the flexible display panel 310.A plurality of pad terminals 317 may be located at the PA 316. The padterminals 317 may be connected to wirings 318 extending from the AA 313.

The driving portion 350 includes a driving circuit, and may be achip-on-film (COF). The driving portion 350 includes a flexible film351, a driving integrated circuit (IC) 352 located on the flexible film351, and a plurality of driving terminals 353 located at an edge of theflexible film 351.

In one embodiment, the driving portion 350 may be a chip-on-plastic(COP) or a chip-on-glass (COG), but is not limited thereto, as long asone or more terminals are located on a flexible film.

The pad terminals 317 may be connected to (e.g., connected to respectiveones of) the driving terminals 353. The driving terminals 353 may bepositioned such that the driving terminals 353 correspond to (e.g.,correspond to respective ones of) the pad terminals 317.

The driving portion 350 may be electrically connected to a circuit board360. The circuit board 360 may be a flexible printed circuit board(FPCB).

The function layer 340 may be located below the second surface 310 b ofthe flexible display panel 310. The function layer 340 includes a firstsurface 341 facing the flexible display panel 310, a second surface 342that is opposite to the first surface 341, and a side surface 343connecting the first surface 341 and the second surface 342 (e.g.,connecting the first surface 341 and another surface 345 to be describedbelow). An adhesion layer 372 may be located between the flexibledisplay panel 310 and the function layer 340.

The function layer 340 includes a step portion 344 below which a portionCP1, at which the flexible display panel 310 is connected to the drivingportion 350, is located. The step portion 344 may be formed such thatthe thickness of a portion of the function layer 340 is smaller than thethickness of a remainder of the function layer 340, the thicknessesbeing measured in a direction from the second surface 342 of thefunction layer 340 to the first surface 341 of the function layer 340.That is, a thickness t1 of the step portion 344 may be smaller than athickness t2 between the first surface 341 and the second surface 342 ofthe function layer 340.

In the portion CP1 located below the step portion 344, the padterminal(s) 317 located on the PA 316 of the flexible display panel 310may be connected to the driving terminal(s) 353 located on the drivingportion 350.

The portion CP1, at which the flexible display panel 310 is connected tothe driving portion 350, might not extend beyond the second surface 342of the function layer 340. In one embodiment, a space S exists below thestep portion 344. The portion CP1, at which the flexible display panel310 is connected to the driving portion 350, and a portion CP2, at whichthe driving portion 350 is connected to the circuit board 360, existwithin the space S. The portions CP1 and CP2 do not extend beyond thesecond surface 342 of the function layer 340.

The step portion 344 may include a surface 345 below which an adhesionlayer 373 is located. The PA 316 of the flexible display panel 310, thedriving portion 350, and the circuit board 360 may be attached below theadhesion layer 373.

In one embodiment, the adhesion layer 373 may be located alone betweenthe surface 345 of the step portion 344 and the PA 316, between thesurface 345 of the step portion 344 and the driving portion 350, andbetween the surface 345 of the step portion 344 and the circuit board360. That is, other elements, such as a polymer film having a supportingcapability, might not exist between the surface 345 of the step portion344 and the PA 316, between the surface 345 of the step portion 344 andthe driving portion 350, or between the surface 345 of the step portion344 and the circuit board 360. In one embodiment, the adhesion layer 373may have a varying thickness.

The flexible display panel 310 may extend below the step portion 344while passing by the side surface 343 of the function layer 340. Forexample, the BA 315 allowing the flexible display panel 310 to be foldedin one direction may be located at the side surface 343 of the functionlayer 340. The PA 316 of the flexible display panel 310 extending fromthe BA 315 to an edge of the flexible display panel 310 may be locatedbelow the step portion 344.

A curvature of the BA 315 of the flexible display panel 310 maycorrespond to the thickness t1 of the step portion 344 of the functionlayer 340. The curvature of the flexible display panel 310 may varydepending on the thickness t1 of the step portion 344 of the functionlayer 340. In one embodiment, a radius of the curvature of the BA 315may be in a range of about 0.05 millimeters to about 0.3 millimeters,and a size of bezel may be about 0.3 millimeters or less.

In one embodiment, a support layer may be located between the flexibledisplay panel 310 and the function layer 340.

For example, referring to FIG. 5, a support layer 570 may be locatedbetween a flexible display panel 510 and a function layer 540. Thesupport layer 570, which may fill a distance d between the flexibledisplay panel 510 and the function layer 540, may have a Young's modulusof about 10 MPa or more. The thickness of the support layer 570 may beabout 5 micrometers or less. In other embodiments, the support layer 570may include a material having a Young's modulus of about 10 MPa or less.In other embodiments, the support layer 570 might not include a materialthat has a Young's modulus of more than about 10 MPa, and might not havea thickness of more than about 5 micrometers.

In one or more embodiments, the support layer 570 may be located belowareas of a flexible display device other than the area as describedabove. For example, a support layer having a Young's modulus of about 10MPa and a thickness of about 5 micrometers or less may be located belowthe step portion 344 of the function layer 340 illustrated in FIG. 4. Inone embodiment, a support layer including a material that has a Young'smodulus of more than about 10 MPa and a thickness of more than about 5micrometers might not be located below the step portion 344. In one ormore embodiments, the support layer may include a material having aYoung's modulus of about 10 MPa or less.

The function layer 340 may have a structure including a plurality offilms stacked.

For example, referring to FIG. 6, a function layer 620 may be locatedunder a flexible display panel 610.

The function layer 620 of the present embodiment includes a cushionlayer 623 located between the flexible display panel 610 and the drivingportion 350 (refer to FIG. 4). The cushion layer 623 may reduce animpact that may otherwise be applied to the flexible display panel 610.The cushion layer 623 may include a polymer, such as polypropylene (PP)or polyethylene (PE).

In one embodiment, the cushion layer 623 may include any material thathas a density of about 0.5 g/cm³ or more. The cushion layer 623 may beformed as a foam or gel. In one or more embodiments, the cushion layer623 may include a material having high elastic force, for example,rubber.

An embossing layer 621 may be located between the flexible display panel610 and the cushion layer 623. The embossing layer 621 may have anadhesive capability. The embossing layer 621 may include, or define, aplurality of air discharge holes, or indentations, 626 on a surfacethereof facing the flexible display panel 610.

A black layer 622 may be located between the embossing layer 621 and thecushion layer 623 to prevent exposure of constituting parts, such as thedriving portion 350 (refer to FIG. 4) and the circuit board 360 (referto FIG. 4). The black layer 622 may include a black insulating material.An adhesion layer 627 may be located between the black layer 622 and thecushion layer 623.

A graphite layer 624 may be located under the cushion layer 623. Thegraphite layer 624 may dissipate heat. An adhesion layer 628 may belocated between the cushion layer 623 and the graphite layer 624.

A heat dissipation layer 625 may constitute the outermost layer of thefunction layer 620. The heat dissipation layer 625 may include a metallayer including, for example, copper. The heat dissipation layer 625 mayemit heat that has been generated by the flexible display panel 610toward the outside. An adhesion layer 629 may be located between thegraphite layer 624 and the heat dissipation layer 625.

In one embodiment, any one of the layers that constitute the functionlayer 620 may have a composite functionality.

In one embodiment, referring to FIG. 7, a function layer 720 may belocated under a flexible display panel 710.

The function layer 720 of the present embodiment includes a cushionlayer 723 located between the flexible display panel 710 and the drivingportion 350 (refer to FIG. 4). A cushion layer 723 may have a compositefunctionality. The cushion layer 723 may include a polymer in the formof a foam or a gel to reduce impact otherwise applied to the flexibledisplay panel 710. The density of the foam or gel may be about 0.5 g/cm³or more. In one or more embodiments, the cushion layer 723 may includerubber. The cushion layer 723 may include a material having a Young'smodulus of about 10 MPa or less. In one embodiment, the cushion layer723 may be prepared by mixing graphite particles. In one embodiment, thecushion layer 723 may include a black material.

An embossing layer 721 may be located between the flexible display panel710 and the cushion layer 723. A plurality of air discharge holes, orindentations, 726 may be at a surface of the embossing layer 721 thatfaces the flexible display panel 710.

A heat dissipation layer 725 may constitute the outermost layer of thefunction layer 720. The heat dissipation layer 725 may include a metallayer including, for example, copper. An adhesion layer 729 may belocated between the cushion layer 723 and the heat dissipation layer725.

The function layer 620 illustrated in FIG. 6 and the function layer 720illustrated in FIG. 7 may further include layers for performing otherfunctions. Such layers may include a protection layer for reinforcingstrength of a function layer, an antenna layer, or the like. In one ormore embodiments, the thickness of the function layer 620 illustrated inFIG. 6 and the thickness of the function layer 720 illustrated in FIG. 7may each be appropriately designed depending on a correspondingfunction.

FIG. 8 is a cross-sectional view of a flexible display device 800according to an embodiment, the flexible display device 800 beingassembled.

Referring to FIG. 8, the flexible display device 800 includes a flexibledisplay panel 810, a driving portion 850 that is electrically connectedto the flexible display panel 810, and a function layer 840 locatedbelow the flexible display panel 810.

The flexible display panel 810 includes a first surface 810 a, and asecond surface 810 b that is opposite to the first surface 810 a. Thesecond surface 810 b may face the function layer 840.

A planarizing plate 830 may be located above the flexible display panel810. An adhesion layer 871 may be located between the flexible displaypanel 810 and the planarizing plate 830.

The flexible display panel 810 includes a BA 815 to allow the flexibledisplay panel 810 to bend. In one embodiment, the flexible display panel810 includes a PA 816 extending from the BA 815. The PA 816 may belocated at an edge of the flexible display panel 810. A plurality of padterminals 817 may be located on the PA 816.

The driving portion 850 includes a flexible film 851, a driving IC 852located on the flexible film 851, and a plurality of driving terminals853 located at the edge of the flexible film 851.

The pad terminals 817 may be respectively connected to the drivingterminals 853. The driving terminals 853 may be located in suchpositions that the driving terminals 853 respectively correspond to thepad terminals 817.

The driving portion 850 may be electrically connected to a circuit board860.

The function layer 840 may be located below the second surface 810 b ofthe flexible display panel 810. The function layer 840 includes a firstsurface 841 facing the flexible display panel 810, a second surface 842that is opposite to the first surface 841, and a side surface 843connecting the first surface 841 and the second surface 842 (e.g.,connecting the first surface 841 and another surface 845 to be describedbelow). An adhesion layer 872 may be located between the flexibledisplay panel 810 and the function layer 840.

The function layer 840 includes a step portion 844. The step portion 844may be formed by reducing the thickness of a portion of the functionlayer 840 to be less than the thickness of a remainder of the functionlayer 840 that is in a direction from the second surface 842 of thefunction layer 840 to the first surface 841 of the function layer 840.

A portion CP1 in which the pad terminals 817 of the flexible displaypanel 810 are connected to the driving terminals 853 of the drivingportion 850 may be located below the step portion 844. In oneembodiment, in the portion CP1, the pad terminals 817 of the flexibledisplay panel 810 are connected to the driving terminals 853 of thedriving portion 850, and the portion CP1 does not extend beyond thesecond surface 842 of the function layer 840.

An adhesion layer 873 may be located below a surface 845 of the stepportion 844. The PA 816 of the flexible display panel 810, the drivingportion 850, and the circuit board 860 may be fixed below the adhesionlayer 873.

The flexible display panel 810 may extend below the step portion 844,passing by the side surface 843 of the function layer 840. The BA 815,which allows the flexible display panel 810 to bend in one direction,may be located on the side surface 843 of the function layer 840.

The function layer 840 may support the BA 815. An extension portion 846may extend from the side surface 843 of the function layer 840. Theextension portion 846 may extend from, and may be integrated with, theside surface 843 of the function layer 840. The extension portion 846may have an edge 847 that directly contacts an inner surface 815 a ofthe BA 815. A curvature of an edge 847 of the extension portion 846 maybe the same as a curvature of the BA 815.

As described above, the BA 815 may be supported by adjusting the lengthof the function layer 840.

FIG. 9 is a cross-sectional view of a flexible display device 900according to an embodiment, the flexible display device 900 beingassembled.

Referring to FIG. 9, the flexible display device 900 includes a flexibledisplay panel 910, a driving portion 950 electrically connected to theflexible display panel 910, and a function layer 940 located below theflexible display panel 910.

The flexible display panel 910 includes a first surface 910 a, and asecond surface 910 b that is opposite to the first surface 910 a. Thesecond surface 910 b may face the function layer 940.

A planarizing plate 930 may be located above the flexible display panel910. An adhesion layer 971 may be located between the flexible displaypanel 910 and the planarizing plate 930.

The flexible display panel 910 may have a BA 915 that allows theflexible display panel 910 to bend. In one embodiment, the flexibledisplay panel 910 has a PA 916 extending from the BA 915. The PA 916 maybe located on an edge of the flexible display panel 910. A plurality ofpad terminals 917 may be located on the PA 916.

The driving portion 950 includes a flexible film 951, a driving IC 952located on the flexible film 951, and a plurality of driving terminals953 located at an edge of the flexible film 951.

The pad terminals 917 may be connected to the driving terminals 953. Thedriving terminals 953 may be located in such positions that the drivingterminals 953 correspond to the pad terminals 917.

The driving portion 950 may be electrically connected to a circuit board960.

The function layer 940 may be located below the second surface 910 b ofthe flexible display panel 910. The function layer 940 has a firstsurface 941 facing the flexible display panel 910, a second surface 942that is opposite to the first surface 941, and a side surface 943connecting the first surface 941 and the second surface 942 (e.g.,connecting the first surface 941 and another surface 945 to be describedbelow). An adhesion layer 972 may be located between the flexibledisplay panel 910 and the function layer 940.

The function layer 940 includes a step portion 944. The step portion 944may be formed by reducing the thickness of a portion of the functionlayer 940 in a direction from the second surface 942 of the functionlayer 940 to the first surface 941 of the function layer 940, such thatthe thickness of the thinned portion of the function layer 940 is lessthan that of the remainder of the function layer 940. The portion CP1 inwhich the pad terminals 917 of the flexible display panel 910 areconnected to the driving terminals 953 of the driving portion 950 may belocated below the step portion 944.

An adhesion layer 973 may be located below a surface 945 of the stepportion 944. The PA 916 of the flexible display panel 910, the drivingportion 950, and circuit board 960 may be fixed below the adhesion layer973.

The flexible display panel 910 may extend below the step portion 944while passing by the side surface 943 of the function layer 940. The BA915 of the flexible display panel 910 to be folded in one direction maybe located on the side surface 943 of the function layer 940.

There may be a space between the BA 915 of the flexible display panel910 and the side surface 943 of the function layer 940. A fillingmaterial 980 may fill the space defined by an inner surface 915 a of theBA 915 of the flexible display panel 910 and the side surface 943 of thefunction layer 940. The filling material 980 may be resin. Because thefilling material 980 fills the space between the BA 915 and the functionlayer 940, the BA 915 of the flexible display panel 910 may be fixed.

FIG. 10 is a cross-sectional view of a sub-pixel of an organiclight-emitting display device 1000 according to an embodiment.

Referring to FIG. 10, the organic light-emitting display panel 1000includes a display substrate 1011, and a thin-film encapsulation layer1040 located above the display substrate 1011.

In one embodiment, one sub-pixel may include at least one thin filmtransistor TFT and an organic light-emitting device OLED. A thin filmtransistor is not limited to the thin film transistor TFT illustrated inFIG. 10, and the number and structure of thin film transistors may vary.

The display substrate 1011 may be a flexible glass substrate or aflexible polymer substrate. The display substrate 1011 may betransparent, semi-transparent, or non-transparent.

A buffer film 1012 may be located on the display substrate 1011. Thebuffer film 1012 may completely cover the surface of the displaysubstrate 1011. The buffer film 1012 may include an inorganic materialor an organic material. The buffer film 1012 may be a single film or amulti-layered film.

A thin film transistor TFT may be located on the buffer film 1012. Inthe present embodiment, the thin film transistor TFT may be a top gatetransistor. However, in one or more embodiments, the thin filmtransistor TFT may be a bottom gate transistor.

A semiconductor active material layer 1013 may be located on the bufferfilm 1012. The semiconductor active material layer 1013 may include asource area 1014 and a drain area 1015, which are formed by doping withan N-type impurity ion or a P-type impurity ion. A channel area 1016that is not doped with an impurity may be located between the sourcearea 1014 and the drain area 1015. The semiconductor active materiallayer 1013 may include an organic semiconductor, an inorganicsemiconductor, or amorphous silicon. In one embodiment, thesemiconductor active material layer 1013 may include an oxidesemiconductor.

A gate insulating film 1017 may be deposited on the semiconductor activematerial layer 1013. The gate insulating film 1017 may be an inorganicfilm. The gate insulating film 1017 may be a single film or amulti-layered film.

A gate electrode 1018 may be located on the gate insulating film 1017.The gate electrode 1018 may include a metallic material having excellentconductivity. The gate electrode 1018 may be a single film or amulti-layered film.

An interlayer insulating film 1019 may be located on the gate electrode1018. The interlayer insulating film 1019 may be an inorganic film or anorganic film.

A source electrode 1020 and a drain electrode 1021 may be located on theinterlayer insulating film 1019. In one embodiment, a portion(s) of thegate insulating film 1017 and a portion(s) of the interlayer insulatingfilm 1019 are removed to form contact holes, through which the sourceelectrode 1020 is electrically connected to the source area 1014, andthrough which the drain electrode 1021 is electrically connected to thedrain area 1015.

A passivation film 1022 may be located on the source electrode 1020 andthe drain electrode 1021. The passivation film 1022 may be an inorganicfilm or an organic film. A planarization film 1023 may be located on thepassivation film 1022. The passivation film 1022 or the planarizationfilm 1023 may not be used herein.

The thin film transistor TFT may be electrically connected to theorganic light emitting display device OLED.

The organic light-emitting device OLED may be located on theplanarization film 1023. The organic light-emitting device OLED includesa first electrode 1025, an intermediate layer 1026, and a secondelectrode 1027.

The first electrode 1025 may act as an anode, and may include variousconductive materials. The first electrode 1025 may include a transparentelectrode or a reflective electrode.

A pixel-defining layer 1024 may be located on the planarization film1023. The pixel-defining layer 1024 may cover a portion(s) of the firstelectrode 1025. The pixel-defining layer 1024 defines an emission areaof a sub-pixel by surrounding an edge of the first electrode 1025. Thefirst electrode 1025 may be patterned corresponding to a sub-pixel. Thepixel-defining layer 1024 may include an organic film or an inorganicfilm. The pixel-defining layer 1024 may be a single film or amulti-layered film.

The intermediate layer 1026 may be located on a portion of the firstelectrode 1025 that is exposed by etching a portion of thepixel-defining layer 1024. The intermediate layer 1026 may be formed byusing a deposition process. The intermediate layer 1026 may include anorganic emission layer.

In one or more embodiments, the intermediate layer 1026 may include anorganic emissive layer, and at least one layer of a hole injection layer(HIL), a hole transport layer (HTL), an electron transport layer (ETL),or an electron injection layer (EIL). The present embodiment, however,is not limited thereto. In one or more embodiments, the intermediatelayer 1026 may include, in addition to the organic emission layer,various other function layers.

The second electrode 1027 may be located on the intermediate layer 1026.The second electrode 1027 may act as a cathode. The second electrode1027 may include a transparent electrode or a reflective electrode.

In one embodiment, a plurality of sub-pixels may be located on thedisplay substrate 1011. For example, each of the sub-pixels may embodyred, green, blue, or white color. However, embodiments of the presentdisclosure are not limited thereto.

The thin-film encapsulation layer 1040 may cover the organiclight-emitting device OLED. The thin-film encapsulation layer 1040 mayinclude an inorganic film 1041 and an organic film 1042, which arealternately stacked. For example, the inorganic film 1041 may include afirst inorganic film 1043, a second inorganic film 1044, and a thirdinorganic film 1045, while the organic film 1042 may include a firstorganic film 1046 and a second organic film 1047.

A flexible display device according to an embodiment may have a bezelthat is reduced due to a decrease in the curvature of a bending area ofa flexible display panel. Effects of the present disclosure may furtherinclude, in addition to the above-described effects, other effects thatare obtainable in explaining embodiments of the present disclosure inconnection with the drawings.

It should be understood that embodiments described herein should beconsidered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments.

While one or more embodiments have been described with reference to thefigures, it will be understood by those of ordinary skill in the artthat various changes in form and details may be made therein withoutdeparting from the spirit and scope as defined by the following claimsand their functional equivalents.

What is claimed is:
 1. A flexible display device comprising: a flexible display panel comprising: a display substrate including: an active area; and a non-active area extending outside the active area and including a pad area and a bending area to be folded between the active area and the pad area; a thin film encapsulation layer on a first surface of the display substrate; a driving portion; and a function layer below a second surface opposite to the first surface of the display substrate, wherein the function layer includes a step portion having a first thickness and a second thickness greater than the first thickness, and wherein a curvature of the bending area corresponds to the first thickness of the function layer.
 2. The flexible display device of claim 1, wherein the function layer comprises: a first surface facing the flexible display panel; a second surface opposite to the first surface; and a side surface connecting the first surface and the second surface, wherein a thickness of the step portion corresponds to the first thickness that is less than the second thickness of the functional layer in a direction from the second surface to the first surface of the functional layer.
 3. The flexible display device of claim 2, wherein a pad terminal on the flexible display panel is connected to a driving terminal on the driving portion below the step portion.
 4. The flexible display device of claim 3, wherein a portion at which the flexible display panel is connected to the driving portion does not extend beyond the second surface of the function layer.
 5. The flexible display device of claim 3, wherein the driving portion comprises: a flexible film; and a driving integrated circuit (IC) located on the flexible film, wherein the driving terminal is located at an edge of the flexible film and corresponds to the pad terminal.
 6. The flexible display device of claim 3, wherein a portion of the flexible display panel passes by the side surface of the function layer.
 7. The flexible display device of claim 6, wherein the function layer comprises an extension portion extending from the side surface of the function layer, and contacting an inner surface of the flexible display panel at the bending area.
 8. The flexible display device of claim 7, wherein a curvature of an edge of the extension portion corresponds to a curvature of the flexible display panel at the bending area.
 9. The flexible display device of claim 6, wherein a filling material fills a space between the flexible display panel at the bending area and the side surface of the function layer.
 10. The flexible display device of claim 1, further comprising a support layer between the flexible display panel and the function layer.
 11. The flexible display device of claim 10, wherein a Young's modulus of the support layer is 10 MPa or more, and wherein a thickness of the support layer is about 5 micrometers or less.
 12. The flexible display device of claim 1, wherein the flexible display panel is bent away from the thin film encapsulation layer at the bending area. 